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Asked: 2026-05-19T01:05:52+00:00

This is only marginally programming related – has much more to do w/ colors

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This is only marginally programming related – has much more to do w/ colors and their representation.

I am working on a very low level app. I have an array of bytes in memory. Those are characters. They were rendered with anti-aliasing: they have values from 0 to 255, 0 being fully transparent and 255 totally opaque (alpha, if you wish).

I am having trouble conceiving an algorithm for the rendering of this font. I’m doing the following for each pixel:

            // intensity is the weight I talked about: 0 to 255
            intensity = glyphs[text[i]][x + GLYPH_WIDTH*y];
            if (intensity == 255)
                continue; // Don't draw it, fully transparent
            else if (intensity == 0) 
                setPixel(x + xi, y + yi, color, base); // Fully opaque, can draw original color
            else { // Here's the tricky part
                // Get the pixel in the destination for averaging purposes
                pixel = getPixel(x + xi, y + yi, base);
                // transfer is an int for calculations
                transfer = (int)  ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.red + (float) pixel.red)/2); // This is my attempt at averaging
                newPixel.red = (Byte) transfer;
                transfer = (int)  ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.green + (float) pixel.green)/2);
                newPixel.green = (Byte) transfer;
                // transfer = (int) ((float) ((float) 255.0 - (float) intensity)/255.0 * (((float) color.blue) + (float) pixel.blue)/2);
                transfer = (int)  ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.blue + (float) pixel.blue)/2);
                newPixel.blue = (Byte) transfer;
                // Set the newpixel in the desired mem. position
                setPixel(x+xi, y+yi, newPixel, base);
            }

The results, as you can see, are less than desirable. That is a very zoomed in image, at 1:1 scale it looks like the text has a green “aura”.

The test, less than great

Any idea for how to properly compute this would be greatly appreciated.

Thanks for your time!

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1 Answer

  1. Editorial Team

    You need to blend the background and foreground colours. A-la:

    pixelColour = newColour * intensity + backgroundColour * (1 - intensity)

    By the way, this is a really slow way of rendering and blending fonts. You should instead render all the characters of the font to an off-screen surface with all the properties you need, and then use that as a texture to render to other surfaces when you need text.

    Edit:

    This doesn’t look right:

    (255.0 - (float) intensity/255.0)

    It should instead be:

    (255.0 - (float) intensity)/255.0
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